Writing implement

ABSTRACT

A writing implement, wherein elements forming a reverse flow prevention mechanism are formed in rather simple shapes and assembly process for the reverse flow prevention mechanism is rather simplified. The reverse flow prevention mechanism ( 19 ) comprises a valve chamber ( 54   b ), an inflow port ( 55 ) opened to the ink storage part ( 16 ) side of the valve chamber ( 54   b ), an outflow port ( 56 ) opened to the writing tip ( 17 ) side of the valve chamber ( 54   b ), a valve element ( 57 ) stored in the valve chamber ( 54   b ), a restricting body ( 58 ) stored in the valve chamber ( 54   b ) at a position on the outflow port ( 56 ) side of the valve element ( 57 ), and a valve seat ( 54   c ) formed around the inflow port ( 55 ). When the writing tip ( 17 ) is faced upward, the inflow port ( 55 ) is closed by the valve element ( 57 ), and when faced downward, the valve element ( 57 ) is allowed to touch the restricting body ( 58 ) and does not reach the outflow port ( 56 ).

This application is a 371 of international applicationPCT/JP2004/010326, which claims priority based on Japanese patentapplication No. 2003-300225 filed Aug. 25, 2003, which is incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to a writing implement, more particularlyto a writing implement having a reverse flow prevention mechanism forink.

BACKGROUND ART

Conventionally, as a writing implement having a reverse flow preventionmechanism for ink, for example, a ballpoint pen disclosed in JP 04-52067Y or JP 3197422 B is known. Hereinafter, explanation is made referringto both FIG. 8 illustrating the former prior art and FIG. 9 illustratingthe latter one. Here, the figures referred to in the followingexplanation are all described in these FIGS. 8 and 9.

A ballpoint pen 100 disclosed in JP 04-52067 Y, as illustrated in FIG.8, comprises an ink storage tube 110, a joint 120 fixed to a front endof the ink storage tube 110, and a tip 130 fixed to a front end of thejoint 120.

In a center of the joint 120 is provided a valve chamber 121. In frontof the valve chamber 121 is provided a tip fixing hole 122 penetratingfrom the valve chamber 121 to the front end of the joint 120. In rear ofthe valve chamber 121 is provided an ink storage tube fixing hole 123penetrating from the valve chamber 121 to a rear end of the joint 120.

At a rear part of the valve chamber 121 is provided a valve seat 124. Onan inner surface of a front part of the valve chamber is provided aplurality of protrusions 125 protruding inward of the valve chamber 121.

The joint 120 is molded integrally of elastically deformable resincomposition.

In the valve chamber 121 is stored a spherical valve element 126. Thevalve element 126 can move in the valve chamber 121 by its own weightand cannot slip out of the valve chamber 121.

A rear end part of the tip 130 is pressed into and fixed to the tipfixing hole 122. A front end of the ink storage tube 110 is pressed intoand fixed to the ink storage tube fixing hole 123.

When the tip 130 is faced upward, the valve element 126 falls toward theink storage tube 110 by its own weight and touches a whole circumferenceof the valve seat 124. Thereby, reverse flow of ink is prevented.

On the other hand, when the tip 130 is faced downward, the valve element126 falls toward the tip 130 by its own weight and is caught by theprotrusions 125. Thereby, the ink is supplied to the tip 130 throughgaps between the protrusions 125.

On the other hand, a ballpoint pen 100 disclosed in JP 3197422 B, asillustrated in FIG. 9, comprises an ink storage tube 110, a joint 120fixed to a front end of the ink storage tube 110, and a tip 130 fixed toa front end of the joint 120.

In a center of the joint 120 is provided a valve chamber 121. In frontof the valve chamber 121 is provided a tip fixing hole 122 penetratingfrom the valve chamber 121 to the front end of the joint. In rear of thevalve chamber 121 is provided a guiding hole 127 penetrating from thevalve chamber 121 to a rear end of the joint.

At a rear part of the valve chamber 121 is provided a valve seat 124.

In the valve chamber 121 is stored a spherical valve element 126. Thevalve element 126 can move in the valve chamber 121 by its own weightand cannot slip out of the valve chamber 121.

A rear end of the tip 130 is pressed into and fixed to the tip fixinghole 122.

A rear end of the joint 120 is pressed into and fixed to a front end ofthe ink storage tube 110.

An intervening piece 140 is inserted forcibly and fixed between thevalve element 126 and the rear end of the tip 130. At a rear end of theintervening piece 140 is provided ink grooves 141. Ink can pass throughthe ink grooves 141 when the valve element 126 touches the rear end ofthe intervening piece 140.

In the tip 130 is stored a spring 150. A rear end of the spring 150touches a front end of the intervening piece 140. A front end of thespring 150 touches a rear end of a ball 131 held by a front end of thetip 130.

When writing is not performed, the ball 131 is pressed onto an innersurface of a bent portion by being pushed by the spring 150.

When the tip 130 is faced upward, the valve element 126 falls toward theink storage tube 110 by its own weight and touches a whole circumferenceof the valve seat 124. Thereby, reverse flow of the ink is prevented.

On the other hand, when the tip 130 is faced downward, the valve element126 falls toward the tip 130 by its own weight and touches the rear endof the intervening piece 140. Under this condition, the ink is suppliedto the tip 130 through the ink grooves 141. Moreover, though writing isnot performed, a direct flow of the ink is prevented since the ball 131is pressed onto the inner surface of the bent portion by being pushed bythe spring 150.

However, as disclosed in JP 04-52067 Y, when the protrusions areprovided on the inner surface of the valve chamber, a mold structure formolding becomes rather complex since the protrusions make undercuts.Thereby, manufacturing cost for a whole writing implement becomes ratherexpensive. Moreover, since the protrusions make undercuts, the size ofeach protrusion must be made as small as possible. Then, passages forthe ink flow may not be sufficiently secured depending upon a diameterof the ball or a kind of the ink.

Moreover, as disclosed in JP 319422 B, when the intervening piece isfixed between the valve element and the rear end of the tip, a shape ofthe intervening piece becomes complex and highly-developed manufacturingtechnology is necessary for a process of inserting the intervening pieceinto the joint with the intervening piece correctly directed. Namely,very highly-developed manufacturing technology is necessary for aprocess of inserting the intervening piece to be located in apredetermined position in the joint with the ink grooves of theintervening piece being directed backward. Thus, manufacturing cost fora whole writing implement becomes expensive.

Then, the first problem to be solved by the present invention is toprovide a writing implement wherein elements (a valve chamber, etc.)forming a reverse flow prevention mechanism are formed in rather simpleshapes and assembly process for the reverse flow prevention mechanism israther simplified, thereby contributing to reduction of themanufacturing cost.

Moreover, the second problem to be solved by the present invention is,in addition to the first problem, to provide the writing implementwherein the assembly process for the reverse flow prevention mechanismis more simplified.

DISCLOSURE OF INVENTION

In view of the first problem, the present invention is a writingimplement comprising an ink storage part storing ink, a writing tipapplying the ink, an ink guiding hole connecting the ink storage partand the writing tip, and a reverse flow prevention mechanism provided ina midway of the ink guiding hole and preventing reverse flow of the ink;the reverse flow prevention mechanism comprising a valve chamberconsisting of a part of the ink guiding hole, an inflow port opened tothe ink storage part side of the valve chamber and having a smallerinner diameter than that of the valve chamber, an outflow port opened tothe writing tip side of the valve chamber and having a smaller innerdiameter than that of the valve chamber, a valve element stored in thevalve chamber and being movable in the valve chamber by its own weight,a restricting body being stored in the valve chamber at a position onthe outflow port side of the valve element, being formed not to touchthe writing tip, and being formed in a shape not to interrupt an inkflow in the valve chamber and not to close the outflow port, and a valveseat provided around the inflow port; the inflow port being closed bythe valve element falling toward the inflow port by its own weight totouch the valve seat when the writing tip is faced upward; the inflowport being opened by the valve element falling toward the outflow portby its own weight to depart from the valve seat and touching therestricting body not to reach the outflow port when the writing tip isfaced downward.

The “ink storage part” is a part in which the ink is stored.

For example, in case of a writing implement comprising a cylindrical inkstorage tube in which ink is stored, an inner space of the ink storagetube works as the ink storage part.

The “writing tip” is a part for applying the ink. Namely, the writingtip is a part touching a surface to be written.

For example, in case that the writing implement is a ballpoint pen, aball held capable of freely rotating by a front end of a tip works asthe writing tip.

The “ink guiding hole” is a hole that connects the ink storage part andthe writing tip.

For example, in case of a writing implement in which a joint is fixed toa front end of an ink storage tube and a tip is fixed to a front end ofthe joint, i.e., a writing implement in which the ink storage tube andthe tip are fixed through the joint, an integrated hole consisting of apenetrating hole in the joint and a back hole in the tip works as theink guiding hole.

Moreover, in case of a writing implement in which a tip is directlyfixed to a front end of an ink storage tube, a back hole in the tipworks as the ink guiding hole.

The “reverse flow prevention mechanism” is provided for preventingreverse flow of the ink.

The reverse flow prevention mechanism is provided in a midway of the inkguiding hole. Therefore, the reverse flow prevention mechanism may beprovided in a midway of the penetrating hole (i.e., in the joint) or maybe provided in a midway of the back hole (i.e., in the tip).

The reverse flow prevention mechanism comprises the “valve chamber,” the“inflow port,” the “outflow port,” the “valve element,” the “restrictingbody” and the “valve seat.”

At an ink storage tube side of the valve chamber is opened the inflowport. At a writing tip side of the valve chamber is opened the outflowport. The inner diameters of both the inflow port and the outflow portare smaller than that of the valve chamber. Then, the ink flows into thevalve chamber through the inflow port, and the ink in the valve chamberflows out through the outflow port.

In the valve chamber are stored the valve element and the restrictingbody. The valve element is always at a position on the inflow port sideof the restricting body. The restricting body is always at a position onthe outflow port side of the valve element.

The valve element is made to be movable in the valve chamber by its ownweight. Though the valve element is made to be movable in the valvechamber, it never comes to the outflow port side of the restrictingbody.

The restricting body is so formed as not to touch the writing tip. Forexample, in case that the writing implement is a ballpoint pen, therestricting body may touch a holder of the writing tip, but is so formedas not to touch the ball.

The restricting body is so formed in a shape as not to interrupt the inkflow in the valve chamber and not to close the outflow port. In casethat the valve chamber is a round-shaped hole and so is the outflowport, the restricting body is formed, for example, as a rectangularplate-shape whose shorter sides are smaller than the inner diameter ofthe valve chamber and larger than the inner diameter of the outflow portand whose longer sides are larger than the inner diameter of the valvechamber. Thus, the restricting body may be made not to interrupt the inkflow in the valve chamber and not to close the outflow port.

The restricting body is not limited to the rectangular shape and may beformed in any desired shape unless it interrupts the ink flow in thevalve chamber and closes the outflow port.

The valve element may be formed, for example, in a spherical shape or ina wedge shape.

The valve seat is provided around the inflow port and is so formed thatit can be touched by the valve element. In case that the valve elementis spherical shaped, the valve seat may be formed, for example, in atapered shape or in a concaved spherical shape whose inner diametergradually becomes smaller toward the ink storage part side.

When the writing tip is faced upward, the valve element falls toward theinflow port by its own weight. Then, the valve element touches the valveseat and closes the inflow port. Thereby, the reverse flow of the ink isprevented.

On the other hand, when the writing tip is faced downward, the valveelement falls toward the outflow port by its own weight. Then, the valveelement departs from the valve seat and the inflow port is opened. Atthe same time, since the valve element touches the restricting body, itdoes not reach the outflow port. Thereby, since the ink can flow intothe valve chamber through the inflow port and the outflow port is notclosed by the valve element, the ink in the valve chamber can flow outthrough the outflow port to be supplied to the writing tip.

According to the invention, the movement of the valve element toward theoutflow port is prevented by the restricting body. Thereby, it is notnecessary to provide any protrusion on the inner surface of the valvechamber. Moreover, the restricting body may be formed in any desiredshape, e.g., a rectangular shape, etc., unless it interrupts the inkflow in the valve chamber and closes the outflow port. Furthermore,since the restricting body should only be so stored in the valve chamberas to be at a position on the outflow port side of the valve element,does not touch the writing tip and is not formed as a member for eitherpushing or fixing the spring, there is no need for a minute positioning.Therefore, the elements (the valve chamber, etc.) forming the reverseflow prevention mechanism can be formed in rather simple shapes.Moreover, the assembly process for the reverse flow prevention mechanismcan be rather simplified, thereby contributing to reduction of themanufacturing cost.

In view of the second problem, the present invention is, in addition tothe characteristics as described above, characterized in that therestricting body is movable in the valve chamber by its own weight.

According to the invention, since the restricting body is also movablein the valve chamber as well as the valve element, there is no need fora positioning of the restricting body in the valve chamber at all.Namely, the restricting body should only be simply thrown into the valvechamber. Therefore, the assembly process for the reverse flow preventionmechanism can be more simplified.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] a side sectional view of a ballpoint pen as a writing implementaccording to an embodiment of the present invention.

[FIG. 2] a side sectional view of an essential part of a ballpoint penas a writing implement according to an embodiment of the presentinvention.

[FIG. 3] a side sectional view of an essential part of a ballpoint penas a writing implement according to an embodiment of the presentinvention (with a tip faced downward).

[FIG. 4] a sectional view along the A—A line in FIG. 3.

[FIG. 5] a sectional view illustrating a modified embodiment of arestricting body.

[FIG. 6] a sectional view illustrating a modified embodiment of arestricting body.

[FIG. 7] a sectional view illustrating a modified embodiment of arestricting body.

[FIG. 8] a side sectional view of an essential part of a ballpoint penas a conventional writing implement.

[FIG. 9] a side sectional view of an essential part of a ballpoint penas a conventional writing implement.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, explanation is made for a ballpoint pen as a writingimplement according to a present embodiment.

FIG. 1 is a side sectional view of a ballpoint pen 10, FIG. 2 is a sidesectional view of an essential part of the ballpoint pen 10, FIG. 3 is aside sectional view of the essential part of the ballpoint pen 10 (witha tip 40 faced downward), FIG. 4 is a sectional view along the A—A linein FIG. 3, and FIGS. 5 to 7 are sectional views of modified embodimentsof a restricting body 58.

The ballpoint pen 10 as a writing implement according to the presentembodiment comprises a cylindrical shaft tube 15 and a refill 30assembled inside the shaft tube 15.

The refill 30 comprises a cylindrical ink storage tube 31, a joint 50fixed to a front end of the ink storage tube 31 and a tip 40 fixed to afront end of the joint 50.

The ink storage tube 31 is provided for storing ink. Inside the inkstorage tube 31 is stored the ink. Namely, in the present embodiment,the inside of the ink storage tube 31 works as an ink storage part 16.

The joint 50 is provided for connecting the ink storage tube 31 and thetip 40. Namely, the ink storage tube 31 and the tip 40 are fixed throughthe joint 50.

At a rear end of the joint 50 is provided a storage tube fixing part 51for fixing the ink storage tube 31. The storage tube fixing part 51comprises a cylindrical inner tubular part 52 and a cylindrical outertubular part 53 that shares the same centerline with the inner tubularpart 52 and has a larger diameter than that of the inner tubular part52. An outer diameter of the inner tubular part 52 is slightly largerthan an inner diameter of the ink storage tube 31, and an inner diameterof the outer tubular part 53 is slightly smaller than an outer diameterof the ink storage tube 31. Then, a front end part of the ink storagetube 31 is pressed into a gap between the inner tubular tube 52 and theouter tubular tube 53. Thus, the joint 50 is fixed to the front end ofthe ink storage tube 31.

Moreover, in the joint 50 is provided a penetrating hole 54 penetratingfrom a front end to a rear end thereof. The penetrating hole 54 consistsof a tip fixing hole 54 a, a valve chamber 54 b, a valve seat 54 c, alesser guiding hole 54 d and a greater guiding hole 54 e, in an orderfrom its front end. Namely, in an order from the front end of the joint50, the tip fixing hole 54 a, the valve chamber 54 b, the valve seat 54c, the lesser guiding hole 54 d and the greater guiding hole 54 e areintegrated to form the penetrating hole 54. The tip fixing hole 54 a andthe valve chamber 54 b are formed as a round-shaped hole of anapproximately equal inner diameter. Moreover, the valve seat 54 c isformed in a tapered shape whose inner diameter gradually becomes smallertoward the rear end. Moreover, the lesser guiding hole 54 d is formed asa round-shaped hole of the smallest inner diameter in the penetratinghole 54. Moreover, the greater guiding hole 54 e is formed as around-shaped hole of a larger inner diameter than that of the lesserguiding hole 54 d. Moreover, the greater guiding hole 54 e is connectedto the inside of the ink storage tube 31 (i.e., the ink storage part16).

The tip 40 comprises a ball 41 as a writing tip 17 and a holder 42 forholding the ball 41. The holder 42 has a ball house 43 at its front endin which the ball 41 is stored, and also has a back hole 44 thatpenetrates from its rear end to the ball house 43. After the ball 41 isinserted in the ball house 43, the front end of the holder 42 is bent tohold the ball 41 capable of freely rotating at the front end. Moreover,an inner diameter of the back hole 44 becomes smaller stepwise from itsrear end to its front end.

Moreover, around the rear end part of the holder 42 is provided adiminished diameter part 45 of a smaller outer diameter than that of amiddle part of the holder 42. Then, the diminished diameter part 45 ispressed into the tip fixing hole 54 a of the joint 50. In this way, thetip 40 is fixed to the front end of the joint 50.

Moreover, the penetrating hole 54 of the joint 50 and the back hole 44of the holder 42 are integrated to introduce the ink from the inkstorage part 16 to the ball 41 as the writing tip 17. Namely, in thepresent embodiment, an integrated hole consisting of the penetratinghole 54 and the back hole 44 works as an ink guiding hole 18 connectingthe ink storage part 16 and the writing tip 17.

In a midway of the ink guiding hole 18 is provided a reverse flowprevention mechanism 19. The reverse flow prevention mechanism 19 isprovided for preventing reverse flow of the ink. The reverse flowprevention mechanism 19 consists of the valve chamber 54 b, an inflowport 55, an outflow port 56, a valve element 57, a restricting body 58and the valve seat 54 c. The valve chamber 54 b is located in a middleof the joint 50 and consists of a part of the penetrating hole 54 (i.e.,of a part of the ink guiding hole 18). The inflow port 55 is opened tothe ink storage part 16 side of the valve chamber 54 b, and the outflowport 56 is opened to the writing tip 17 side of the valve chamber 54 b.In the present embodiment, an opening at a front end of the lesserguiding hole 54 d works as the inflow port 55, and an opening at a rearend of the back hole 44 works as the outflow port 56. Both the inflowport 55 and the outflow port 56 are of a smaller inner diameter thanthat of the valve chamber 54 b. Then, the ink flows into the valvechamber 54 b through the inflow port 55, and the ink in the valvechamber 54 b flows out through the outflow port 56. Moreover, since theopening at the front end of the lesser guiding hole 54 d works as theinflow port 55, the valve seat 54 c is provided circularly around theinflow port 55.

Moreover, in the valve chamber 54 b is stored the valve element 57 andthe restricting body 58. The valve element 57 is stored at a position onthe inflow port 55 side in the valve chamber 54 b, and the restrictingbody 58 is stored at a position on the outflow port 56 side in the valvechamber 54 b.

The valve element 57 is made of stainless steel in a spherical shape.The diameter of the valve element 57 is smaller than the inner diameterof the valve chamber 54 b and larger than the inner diameter of theinflow port 55. Thus, the valve element 57 is made to be movable in thevalve chamber 54 b by its own weight. Moreover, the valve element 57never slips out of the valve chamber 54 b through the inflow port 55.

The restricting body 58 is made of stainless steel in a rectangularplate-shape. Shorter sides of the restricting body 58 are smaller thanthe inner diameter of the valve chamber 54 b and longer than the innerdiameter of the outflow port 56. Moreover, longer sides of therestricting body 58 are larger than the inner diameter of the valvechamber 54 b. Thus, the restricting body 58 is made to be movable in thevalve chamber 54 b by its own weight, does not interrupt the ink flow inthe valve chamber 54 b and does not close the outflow port 56. Moreover,the restricting body 58 never slips out of the valve chamber 54 bthrough the outflow port 56. Therefore, the restricting body 58 nevercomes into the holder 42 of the tip 40, and never touches the ball 41 asthe writing tip 17.

Moreover, though both the valve element 57 and the restricting body 58are made to be movable in the valve chamber 54 b, the valve element 57is always at a position on the inflow port 55 side of the restrictingbody 58 and the restricting body 58 is always at a position on theoutflow port 56 side of the valve element 57.

Then, when the ball 41 as the writing tip 17 is faced upward, the valveelement 57 falls toward the inflow port 55 by its own weight and touchesa whole circumference of the valve seat 54 c to close the inflow port55. The reverse flow of the ink is prevented thereby.

On the other hand, when the ball 41 as the writing tip 17 is faceddownward, the valve element 57 falls toward the outflow port 56 by itsown weight and departs from the valve seat 54 c to open the inflow port55. At the same time, the restricting body 58 falls toward the outflowport 56 by its own weight and touches the rear end of the holder 42 ofthe tip 40, and the valve element 57 touches the restricting body 58 tobe prevented from reaching the outflow port 56. Thereby, since the inkflows into the valve chamber 54 b through the inflow port 55 and theoutflow port 56 is not closed by the valve element 57, the ink in thevalve chamber 54 b flows out through the outflow port 56 and is suppliedto the ball 41 as the writing tip 17. At this time, though the valveelement 57 departs from the valve seat 54 c, it is prevented by therestricting body 58 from moving toward the outflow port 56 and stays ata position relatively near to the valve seat 54 c. Thus, when the ball41 as the writing tip 17 is turned from downward to upward, a timenecessary for the valve element 57 to touch the valve seat 54 c isrelatively short.

Next, a brief explanation is made to an assembly process of the reverseflow prevention mechanism 19 among the assembly process of the ballpointpen 10 as the writing implement according to the present embodiment.

First, the valve element 57 is thrown into the valve chamber 54 b fromthe front end of the joint 50, and then the restricting body 58 isthrown into the valve chamber 54 b from the front end of the joint 50.After that, the diminished diameter part 45 of the holder 42 of the tip40 is pressed into the tip fixing hole 54 a of the joint 50 and therebythe tip 40 is fixed to the front end of the joint 50.

As explained above, in the present embodiment, the valve element 57 isprevented by the restricting body 58 from moving toward the outflow port56. Thereby, it is not necessary to provide any protrusions on the innersurface of the valve chamber 54 b.

Moreover, the restricting body 58 is formed in a rectangularplate-shape. Thereby, it is very easy to manufacture the restrictingbody 58.

Moreover, in the present embodiment, the restricting body 58 is made tobe movable in the valve chamber 54 b, does not touch the ball 41 as thewriting tip 17, and does not work as a member for pushing or fixing aspring. Thereby, when the restricting body 58 is stored in the valvechamber 54 b, there is no need to insert the restricting body 58forcibly or no need for a minute positioning.

Thus, in the present embodiment, the elements (the valve chamber 54 b,etc.) forming the reverse flow prevention mechanism 19 can be formed inrelatively simple shapes. Moreover, the assembly process for the reverseflow prevention mechanism 19 can be rather simplified, therebycontributing to reduction of the manufacturing cost.

Moreover, in the present embodiment, the shorter sides of therestricting body 58 are larger than the inner diameter of the back hole44. Thus, since the restricting body 58 does not come into the holder 42of the tip 40, the ink flow in the tip 40 is not inhibited and it ispossible to eliminate bubbles smoothly during the manufacture of theballpoint pen 10 as the writing implement.

Moreover, in the present embodiment, when the ball 41 as the writing tip17 is faced downward, though the valve element 57 departs from the valveseat 54 c, it is prevented by the restricting body 58 from moving towardthe outflow port 56 and stays at a position relatively near to the valveseat 54 c. Thus, when the ball 41 as the writing tip 17 is turned fromdownward to upward, a time necessary for the valve element 57 to touchthe valve seat 54 c is relatively short. Therefore, the prevention ofthe reverse flow of the ink can be performed more effectively.

Further, the restricting body 58 can be formed in a shape other than therectangular plate-shape unless the shape interrupts the ink flow in thevalve chamber 54 b and closes the outflow port 56.

For example, as illustrated in FIG. 5(A), the restricting body 58 can beso formed that its perpendicular section to the centerline (i.e., thesame sectional angle as in FIG. 4) may be ring-shaped.

Moreover, for example, as illustrated in FIGS. 5(B), 6(C), 6(D), 6(E),7(F) or 7(G), the restricting body 58 can be so formed that itsperpendicular section to the centerline may display Y-shaped, C-shaped,V-shaped, L-shaped, U-shaped or S-shaped, respectively.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a writing implement with areverse flow prevention mechanism of ink.

1. A writing implement comprising: an ink storage part storing ink, awriting tip applying the ink, an ink guiding hole connecting said inkstorage part and said writing tip, and a reverse flow preventionmechanism provided in a midway of said ink guiding hole and preventingreverse flow of the ink; said reverse flow prevention mechanismcomprising: a valve chamber consisting of a part of said ink guidinghole, an inflow port opened to the ink storage part side of said valvechamber and having a smaller inner diameter than that of the valvechamber, an outflow port opened to the writing tip side of said valvechamber and having a smaller inner diameter than that of the valvechamber, a valve element stored in said valve chamber and being movablein the valve chamber by its own weight, a restricting body being storedin said valve chamber at a position on the outflow port side of saidvalve element, being formed not to touch said writing tip, and beingformed in a shape not to interrupt an ink flow in the valve chamber andnot to close said outflow port, and being movable in said valve chamberby its own weight, and a valve seat provided around said inflow port;said inflow port being closed by said valve element falling toward theinflow port by its own weight to touch said valve seat when said writingtip is faced upward; said inflow port being opened by said valve elementfalling toward said outflow port by its own weight to depart from saidvalve seat and touching said restricting body not to reach the outflowport when said writing tip is faced downward.